/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.tsfile.encoding.encoder;

import org.apache.iotdb.tsfile.file.metadata.enums.TSEncoding;

import java.io.ByteArrayOutputStream;

/**
 * Gorilla encoding. For more information about how it works, please see
 * http://www.vldb.org/pvldb/vol8/p1816-teller.pdf
 */
public abstract class GorillaEncoderV1 extends Encoder {

    // flag to indicate whether the first value is saved
    protected boolean flag;
    protected int leadingZeroNum;
    protected int tailingZeroNum;
    // 8-bit buffer of bits to write out
    protected byte buffer;
    // number of bits remaining in buffer
    protected int numberLeftInBuffer;

    protected GorillaEncoderV1() {
        super(TSEncoding.GORILLA_V1);
        this.flag = false;
    }

    protected void writeBit(boolean b, ByteArrayOutputStream out) {
        // add bit to buffer
        buffer <<= 1;
        if (b) {
            buffer |= 1;
        }

        // if buffer is full (8 bits), write out as a single byte
        numberLeftInBuffer++;
        if (numberLeftInBuffer == 8) {
            clearBuffer(out);
        }
    }

    protected void writeBit(int i, ByteArrayOutputStream out) {
        writeBit(i != 0, out);
    }

    protected void writeBit(long i, ByteArrayOutputStream out) {
        writeBit(i != 0, out);
    }

    protected void clearBuffer(ByteArrayOutputStream out) {
        if (numberLeftInBuffer == 0) {
            return;
        }
        if (numberLeftInBuffer > 0) {
            buffer <<= (8 - numberLeftInBuffer);
        }
        out.write(buffer);
        numberLeftInBuffer = 0;
        buffer = 0;
    }

    protected void reset() {
        this.flag = false;
        this.numberLeftInBuffer = 0;
        this.buffer = 0;
    }
}
